When considering the establishment of an aquaculture farm it is vitally important that you research every aspect of the enterprise thoroughly. The first part of your information gathering stage should be the collation of a detailed list of all the factors that are likely to influence your operation.
You should also decide on the scale of your venture and determine what is your reason for going into aquaculture. Is it for fun, perhaps a sideline to an existing farm? Providing it returns a wage, profits don’t need to be maximised.
Is it a company seeking maximum profit, tax loss or input to another part of the company?
Perhaps you want to build fish-out ponds as a tourist attraction or just want to rear juveniles to sell to other farmers, bait suppliers or to the aquarium trade.
Whatever your aims the most important factor to consider is a correct site. The correct siting of a crayfish farm is of the utmost importance in determining its biological, practical and economic feasibility.
The vital considerations for successful realisation of this objective may be classified under three broad headings:
- Water - quantity and quality available and cost of supply.
- Topography and soil characteristics - as they affect water retention, access, security from flooding, design and construction of ponds, buildings and other installations.
- Geographic location - in relation to markets, transport routes, power supply, communications and other faculties.
Competent development planning makes optimum use of the site and avoids bad design features that can affect the economy and viability of the venture permanently.
Water:
The basic factors to consider with regard to water are abundance, source and quality.
Abundance:
A regular, abundant water supply is absolutely essential. Ponds will often need to be emptied and refilled, either for regular maintenance or for some emergency. Also, during the summer months, ponds will lose water through evaporation and will need to be topped up regularly.
Data on rates of evaporation for specific areas is available from the Bureau of Meteorology.
Source:
Water for farm ponds can be drawn from many sources including run-off, rivers, creeks, swamps, underground (bore water) or mains. The layout, size, location and topography of a farm may determine the best or most practical source of water.
- If you are using water that has come to your property by way of run-off or a stream, make sure that it is free of any agricultural or industrial pollutants from neighbouring farms.
- Bore water has its advantages. It is a regular, dependable supply, free from fish and other aquatic organisms but can be too saline in some areas and should be checked before using.
- Mains water from domestic supplies is considered too expensive to be used in aquaculture.
The cost of supplying water to the site may be a major factor in determining the economic feasibility of a pond farm. Pumping costs can be minimised by designing the layout of the farm to incorporate a gravity flow system to the ponds from a large holding reservoir.
Quality:
The following are the most important parameters when considering water quality. Equipment for testing water quality can be purchased from any of a number of laboratory suppliers.
- Water temperature: Each species possess optimum temperatures at which they grow. It is important that you are well aware of the temperature range at which your selected species will survive and thrive. Too low temperatures will result in low growth rates and too high will result in mortalities. If water has to be taken from deep storage dams it should be drawn from the surface. Temperature stratification in a large dam may mean the bottom water is too cold and lacks oxygen. The temperature of ground water increases with the depth of the bore.
- Dissolved oxygen: Different species will have different oxygen requirements. For example yabbies withstand low levels of oxygen in comparison to trout which require higher levels. The influence of dissolved oxygen concentrations on growth is not fully understood, but it is recommended that oxygen levels be maintained above 4 milligrams per litre to ensure good growth.
- Salinity: Testing the saltiness of your water is important when deciding what species to culture. Freshwater crayfish can tolerate high levels of up to 15 ppt however their growth is impeded if levels reach above 5 to 6 ppt. Native finfish such as Murray cod, Callop, Silver perch are able to withstand and grow in salinity levels of up to 10 ppt. Both barramundi, trout and black bream can tolerate both fresh and salty water. There is also some research investigating the potential to use inland saline ground water to culture marine species such as snapper and mulloway.
- pH: A slightly alkaline water with a pH of between 7.5 and 8.5 is recommended. In acid waters (pH below 7.0), crayfish will tend to have soft shells. At these levels fungal diseases can occur and the natural food in the pond is reduced.
- Calcium: Soft water, as indicated by low dissolved calcium levels, causes crayfish to have thin soft shells and reduced growth and survival. It’s recommended that the concentration of calcium in the water for farming should be over 50 milligrams per litre and never below 20 milligrams per litre.
- Turbidity: Turbidity reduces bottom water temperatures, provides protection from predators and allows the stock to feed throughout the day.
- Pollutants: Water contaminated by heavy metals, pesticides, petroleum products or any other pollutants should be avoided.
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